1. Field of the Invention
The present invention relates to lawn mowing and mulching devices. More particularly, the present invention relates to a cutter head for use with a non-rotary, power lawn mower.
2. Discussion of Background
Lawn mowers are well known devices used for cutting grass to maintain the appearance of an area. There are many types of lawn mowers, including rotary mowers and reel mowers. Lawn mowers featuring additional functions, such as mulching, collecting grass clippings, and the like, are also well known. Additionally, many different cutting blades or cutter heads are known for use with lawn mowing devices.
The most widely known lawn mower in use is the power rotary lawn mower having a single rotating blade with cutting edges at opposing distal ends of the blade. The cutting blade rotates at a high speed within a circular housing to both cut the grass and create an upward draft to urge the blades of grass to stand upward for better cutting. The power mower housing functions to prevent injury to the user and to control the direction of discharge of grass clippings and other debris encountered during mower operation.
Normally, the cutting blade is centrally mounted on a shaft extending vertically through the housing from a gasoline or electric powered motor secured on the top of the housing. The motor causes the cutting blade to be rotated at high speeds, clipping the grass immediately under the housing.
Different rotary cutting blade configurations for power lawn mowers are used for a variety of reasons. For example, Burnell, in U.S. Pat. No. 5,019,113, discloses a rotary lawn mower blade assembly having easily detachable replacement blades. Mensing, in U.S. Pat. No. 4,532,708, discloses a blade assembly with a plurality of cutting segments arranged end to end for improved cutting. Also, in U.S. Pat. No. 3,964,243, Knipe features a rotary cutting blade with detachable tines used to blow grass clippings from the mower path.
Mullet, et al., in U.S. Pat. No. 4,916,887, discloses a rotary mulching mower. The mower has a plurality of cutting blades rotatably positioned in a housing for producing mulch. Each cutting blade rotates through a different plane within the housing for cutting the grass clippings into a fine mulch.
The most significant problem with conventional rotary mowers is the inherent danger presented by a high-speed whirling blade. The blade is a direct threat if the user comes into contact with it, and an indirect threat if it propels an object from the housing. Furthermore, because the blade must be exposed to the grass, even the housing that covers it to protect the user is of no help if the mower overturns. Numerous safety features attempt to minimize the threat of direct and indirect injury from the blade.
Several problems exist with current rotary lawn mowers having rotary blades. Rocks, limbs, roots and other foreign debris entering the housing can damage the rotary blades or be suddenly propelled from the housing. Also, the blades become extremely dull and tend to rip and tear the grass rather than cut it cleanly. In sandy soil, the blades erode very rapidly. Thus, the blades have to be frequently replaced or sharpened.
In tall grass, a conventional mower bends the grass as the mower housing passes over it. If the grass is very long, the housing will hold it to the ground so that it is not cut.
Another problem with current rotary lawn mowers is the relatively slow speed at which the mower can travel across a lawn or other grassy areas to be cut. Even when rotating at high speeds, a single blade with 2 cutting edges requires the lawn mower to travel at very low speeds. Thus, it takes a substantial amount of time to mow large areas of grass.
Grass tends to spread either horizontally or vertically. Current lawn mowers only cut vertically growing grasses doing nothing to help cut the horizontally growing stems. By not cutting these stems, thatching problems occur in lawns of certain type grass.
In U.S. Pat. No. 5,261,217, I disclose an innovative design for a non-rotary power lawn mower that eliminates many of these problems. My mower uses multiple blades to aid in the mulching of the cut grass, and also partially encloses these blades to increase the safety of the apparatus. The blades are enclosed in fingers extending parallel to the direction of the motion of the mower. These fingers do not bend the grass down as it enters the cutting area and thus allows a full cut of the grass blade to be made. This design has a number of parts, however, that must be aligned in manufacturing.
There remains a need for a lawn mower that addresses the problems of rotary lawn mowers and is simple to manufacture and assemble.